Aromatization of cyclohexenes and cyclohexadienes with selenium dioxide-trimethylsilyl polyphosphate
摘要:
Selenium dioxide is depolymerized and activated by trimethylsilyl polyphosphate in carbon tetrachloride. The reagent effectively aromatizes substituted cyclohexenes and cyclohexadienes under mild reaction conditions.
Stereochemistry of Hydrodenitrogenation: The Mechanism of Elimination of the Amino Group from Cyclohexylamines over Sulfided Ni–Mo/γ-Al2O3 Catalysts
作者:Fabio Rota、Vidyadhar S Ranade、Roel Prins
DOI:10.1006/jcat.2001.3218
日期:2001.6
cyclohexylamines occurs primarily by means of a β eliminationmechanism. Elimination of a β hydrogen atom attached to a tertiary carbon atom is faster than that of a β hydrogen atom attached to a secondary carbon atom. The rate of elimination also depended on the stereochemical configuration of the amino group with respect to the β hydrogen atoms. Elimination was more rapid when the configuration of the
Hydrogenation of arenes and N-heteroaromatic compounds over ruthenium nanoparticles on poly(4-vinylpyridine): a versatile catalyst operating by a substrate-dependent dual site mechanism
作者:Minfeng Fang、Nataliya Machalaba、Roberto A. Sánchez-Delgado
DOI:10.1039/c1dt10801h
日期:——
A nanostructured catalyst composed of Ru nanoparticles immobilized on poly(4-vinylpyridine) (PVPy) has been synthesized by NaBH4 reduction of RuCl3·3H2O in the presence of the polymer in methanol at room temperature. TEM measurements show well-dispersed Ru nanoparticles with an average diameter of 3.1 nm. Both powder XRD patterns and XPS data indicate that the Ru particles are predominantly in the zerovalent state. The new catalyst is efficient for the hydrogenation of a wide variety of aromatic hydrocarbons and N-heteroaromatic compounds representative of components of petroleum-derived fuels. The experimental data indicate the existence of two distinct active sites in the nanostructure that lead to two parallel hydrogenation pathways, one for simple aromatics involving conventional homolytic hydrogen splitting on Ru and a second one for N-heteroaromatics taking place via a novel heterolytic hydrogen activation on the catalyst surface, assisted by the basic pyridine groups of the support.
Synthesis of olefins from sterically hindered alcohols by pyrolysis of thiocarbonate O-esters
作者:H. Gerlach、Tran Thi Houng、W. Müller
DOI:10.1039/c39720001215
日期:——
Stericallyhindered alcohols e.g.(I; R = H) were acylated with O-4-methylphenyl chlorothioformate in high yield and the resulting thiocarbonates were converted into olefins by pyrolysis.
用O -4-甲基苯基氯硫代甲酸酯将位阻受阻的醇(如(I; R = H))酰化,并通过热解将所得的硫代碳酸酯转化为烯烃。
Diastereoselective Epoxidation of Cyclohexene Derivatives by Dioxiranes Generated in Situ. Importance of Steric and Field Effects
作者:Dan Yang、Guan-Sheng Jiao、Yiu-Chung Yip、Man-Kin Wong
DOI:10.1021/jo9821978
日期:1999.3.1
In this paper, diastereoselective epoxidation of substituted cyclohexenes (substrates 1-7) by dioxiranes generated in situ from ketones and Oxone was systematically investigated. The results revealed that the diastereoselectivity was determined by the steric and field effects of both dioxiranes and substrates, and high diastereoselectivity can be achieved by tuning the ketone structure. Among the ketones
A Novel Epoxidation Reaction of Olefins Using a Combination of Chloramine-M, Benzaldehyde, and Benzyltriethylammonium Chloride
作者:Dan Yang、Chi Zhang、Xue-Chao Wang
DOI:10.1021/ja993472q
日期:2000.5.1
products. Good to excellent diastereoselectivities were obtained for epoxidation of two substitutedcyclohexenes. Chloramine-T was found to give a slower reaction than Chloramine-M. cis-N-Sulfonyloxaziridine D is proposed to be the epoxidizing agent in this novel epoxidation reaction on the basis of the mechanistic studies.